Flat direct view storage tube



Oct. 21, 1969 K, R, HESSE FLAT, DIRECT VIEW STORAGE TUBE Filed July 31, 1967 nited States Patent O 3,473,200 FLAT DIRECT VIEW STORAGE TUBE Kenneth R. Hesse, Fallbrook, Calif., assignor to Hughes Aircraft Company, Culver City, Calif., a corporation of Delaware Filed July 31, 1967, Ser. No. 657,216 Int. Cl. H01j 31/48 US. Cl. 313-68 1 Claim ABSTRACT OF THE DISCLOSURE A compact direct view storage tube is enclosed in a flat generally planar envelope having a neck section along one edge thereof. A single electron gun is located in the neck. A viewing screen is provided on one side of the flat envelope above the neck and gun. First biasing electrodes are provided along the bottom of the envelope to direct the gun produced electron beam vertically. Second biasing electrodes are provided along the Wall of the envelope to re-direct the vertical beam orthogonally to the target. The gun operates in writing, reading and erasure modes.

The invention relates to a direct view storage tube of novel compact design having particular utility in those applications where space is a premium quantity.

Design parameters in many elds, such as in aircraft and other aeronautical applications, has created a demand for small and compact direct view storage tubes. Of course, tube function, resolution and overall quality must not be effectively degraded. In an effort to meet reduced space requirements it has been the practice to reduce the overall length of tube body sections and gun storing neck sections. Some prior art tubes have been produced having an overall length down to eight inches. However, experience has shown that as a result of such miniaturization tube function and picture quality has been substantially degraded over that normally required in some service applications. Thus, the requirement for a compactness, shorter length, coupled with a quality picture, has yet to be eiciently met.

With the above in mind, it is a primary object of the invention to provide a small compact direct view storage tube in which performance quality is not degraded.

It is a further object of the invention to provide a tube of eXtreme compactrless which utilizes a at, generally planar or box-like envelope having the gun structure formed in the general plane of the envelope and along one edge aspect thereof.

It is a further object of the invention to provide a direct view storage tube embodying the structure described and which employs a single electron gun capable of operation in both writing and viewing modes on a timeshared basis.

It is still a further object of the invention to provide a direct view storage tube'of the type described using the described flat, box-like envelope and having appropriate beam deflecting electrodes which control beam position in space in generally perpendicular planes and thereby control beam sweep over the storage and viewing surfaces.

These and other objects of the invention will become apparent in the course of the following description and from an examination of the related drawings, wherein:

FIG. l is a partiallyfragmentary side elevational view of a typical structure employing the invention;

FIG. 2 is a sectional view taken along line 2-2 of FIG. l; and

FIG. 3 is an enlarged detail view of the target used in the invention.

Directing attention to the drawings, a generally at ICC box-like envelope is provided and indicated generally at 12. At one side of the flat envelope 12 a viewing screen 14 is provided, the structure of which will hereinafter be described in detail. The envelope 12 is, of course, hollow and evacuated and is provided with a hollow neck segment 16 adjacent one edge thereof. The neck segment 16 may have disposed therein a conventional electron gun indicated generally at 18 and comprising a conventional cathode assembly 20, as well as electron accelerating structure 22. Appropriate electrical leads 24, 24 project from the neck section 16 to provide means for making desired electrical connections to the cathode and electrode structure described.

The envelope 12 is provided with a plurality of generally parallel vertical deecting elements 26, 26, the latter being positioned along the lower rail wall 28 of the envelope, below and in general alignment with the longitudinal axis of the electron gun 18 as evidenced by the dotted line 21. The line 29 represents the initial line of motion of the electron beam, Further, a plurality of generally parallel horizontal deflecting elements 30, 30 are. positioned along a second wall 32 of envelope 12. That is, the elements 30 are located on an internal aspect of the envelope in opposed relation to the viewing screen 14.

The viewing screen 14 comprises glass plate 34 having a cathode-luminescent phosphor 36 of conventional construction coating the entire inner surface of the plate 34, and an electron permeable aluminum lm 35 backing the entire phosphor area to establish a uniform potential plane at the viewing screen. Adjacent this aluminum film 35 is a storage target, here shown greatly enlarged, and indicated generally by the numeral 40. The target comprises a mesh 41 which may be a conventional high count metallic mesh as shown in the fragmentary section of FIG. l, having mesh openings in the order of 250 to 1,000 openings per linear inch. Completing the target structure, a thin dielectric coating is provided at 42 on the side of the mesh remote from the viewing plate 34. The storage mesh and dielectric coating is of conventional well-known construction and is therefore not further described in detail.

Adjacent the target a collector mesh indicated at 44 is positioned. The collector mesh 44 is also a fine count metallic mesh similar to that described for the storage mesh and is normally slightly spaced from the adjacent surface of the storage mesh. The target 4i) and collector mesh 44 are, of course, generally parallel to and coextensive with the viewing screen 14.

In a preferred mode of tube operation, the cathode 20 of electron gun 18 is brought to a reference potential, such as zero, and an electron beam emanates from the gun as is shown by dotted line 29'. With appropriate biasing, the elements 26 induce the electron beam 29 to move vertically as illustrated by dotted line S0 and the left-right position of -vertical movement may be controlled by appropriate biasing of any one or several of the vertical deflecting elements 26. Thus, the point of vertical deflection of the electron beam 50 can be controllably located with reference to the left-right dimension of the viewing screen 14.

It will be recalled that horizontal deflecting elements 30, 30 are positioned adjacent the wall 32 of envelope 12. As seen in FIG. l, the elements 30 are generally parallel elongated members which are in appropriate spaced relation to the now vertically deflected electron beam 50. By appropriate electrical biasing of the horizontal deflecting elements 30, the vertically deflected beam may be again changed in direction approximately degrees so that the beam is now directed in perpendicular relation to the general plan of the viewing screen 14. This second right angle deflection is illustrated in FIG. 2

priateelectrical biasing of the vertical deflecting elements 26 and the horizontal deilecting elements 30, the electron beam may be moved raster fashion over the entire surfaceof viewing screen 14.

In normal operation, with the cathode at reference potential, an electron beam is created by the application of suitable voltages to the gun electrodes; .'I'he storage surface is brought to beam cutoff potential by erasure, as explained further on. In this condition the storage surface. 42 is at a 0 to y--10 volt potential. To -write a charge pattern on the dielectric surface 42 of the storage target 40, the electrode A41 of the target 40 is pulsed to a potential level such that all levels of the storage material 42 will have a secondary emission ratio greater than unity; that is, 100 to 300 volts, for example, from its normal read potential of approximately l volts.

The electron beam, in the writing mode of tube operation, is conventionally deflected by the elements 25 and 30 and is intensity modulated in response to some external signals. As a result of the beam scanning over the dielectric surface 42 and secondary electron emission of that material, secondary electrons escaping from the dielectric material are collected at collector electrode 44, which may be at a positive potential, for example, 1,000 volts. The potential of the storage surface 41, therefore, is driven in a positive direction by the impinging electron beam and a charge pattern is stored thereon directly beam energy is adjusted so that'v it will operate at a level below the secondary emission first crossover point. This related in amount to the external signals which effect beam modulation. Upon subsequent reduction in the potential of the storage mesh 41 to the read voltage the storage charge pattern remains on the surface of the-dielectric material 42 and is available for subsequent readout.

To effect viewing or readout, the electron beam is biased at a fixed beam current and again scanned over the entire surface of the storage target at a sufficiently fast rate to avoid flicker. In those areas of the target which do not have a charge in the positive direction, the electrons from the beam will be repelled and captured by the collector mesh 44. Where the surface `42 has been charged in a positive direction, a portion of the beam electrons will pass through the mesh openings and impinge on the phosphor surface. The number of electrons transmitted through the mesh at any point is proportional to the charge on the surface at that point. Thus, a legend directly related to the stored charge pattern will appear on the viewing screen.

In addition to the mode of Writing and readout described above, a further mode of dark Writing may be adapted to the tube. To effect dark writing, the mesh 41 is electrically pulsed to approximately 20 volts as in the erasure step. When the electron gun is unblanked and scanned across the surface, electrons strike the storage surface 42 at a velocity which will produce a secondary emission ratio of less than one. The storage surface, accordingly, is charged in a negative or dark direction, toward cathode potential. When the pulse is removed, the dark written areas capacitively follow the pulse and fall to 10 volts. At this voltage, no electrons can penetrate the mesh in the viewing mode so that a dark area is produced.

Readout of the charge pattern may be effected by biasing the viewing screen 36 to a relatively high potential, for example, 10,000 volts. Electrons then passing through the mesh 40 are `accelerated and attracted to the screen 36 and strike the phosphor to create an illumination pattern directly related to the storage pattern on the dielectric 42.

To effect erasure of a given charge pattern, the electron beam is utilized in the same mode as that described for the writing modes of operation above, except that the is accomplished by applying a positive pulse at about l0 volts to the storage mesh. Again, the beam is scanned raster fashion over the entire surface of the target. The effect is to drive the storage material in a negative direction bringing it tothe level of the reference potential; that is, the potential of the cathode. When the storage mesh pulse is removed, the dielectric surfaceA also falls by 10 volts so that a negative charge remains on the surface. f

lFrom the above description it will be apparent to those familiar with this art that a direct View storage tube is provided, extremely compact in structure by virtue of the planar configuration ofthe enclosing envelope and the utilization of a single electron gun on a time-shared basis to effect the several alternate modes of gun operation; that is, optional light or dark writing, as Well as controllable erasure of the charge pattern created during the writing modes of operation.

The invention as disclosed is by wayof illustration and not limitation and may be modified in many respects all within the Aspirit and scope thereof.

What is claimed is:

1. In a direct view storage tube, the combination of a generally flat rectangular sealed and evacuated envelope,

a single electron gun for creating an electron beam positioned in an elongated neck extending from and perpendicular to one edge of the envelope and in the same plane thereof,

a viewing screen on one Wall of the envelope and in a plane generally parallel to thev general plane of the envelope, v

said screen comprising a phosphor coating covering an inner surface of said Wall and having an aluminum film thereon, v

a storage target Vadjacent the coating and comprising a metallic mesh having a dielectric material on the sides thereof remote from the screen,

a collector mesh adjacent the dielectric material,

means to sequentially change the direction of the gun produced electron beam and thereby direct the beam orthogonally to the target and screen,

the last mentioned means comprising a firstx biasing electrode'unit to yfirst direct the beam along an axis generallyy perpendicular to the initial line of motion of the beam,

a second biasing electrode unit to direct the beam along an axis generally perpendicular to the first mentioned axis and toward said screen,

said first biasing electrode being located along one edge of the envelope and in a plane perpendicular to the general plane of the envelope,

said second biasing electrode unit being located on an inner surface of the envelope and along the sides thereof in opposed relation to the screen,

said gun being adapted to be controllably operated in Writing, reading and erasure modes.

References Cited VUNITED STATES PATENTS 2,877,376 3/1959 onhubef 313-92 x 3,155,872 11/1964l Havn et ai 313-77 x 3,284,652 11/1966 Yaggy 313-92 x 3,309,551 3/196-7 Aiken 313-77 x ROBERT SEGAL, Primary Examinert U.s.c1.x.R. 

